Firmware for Alunar M508 3d printer. This is modified off of Marlin 1.1.9 firmware example_configurations/Infitary. These printers appear to be very similar.
To flash the firmware all you have to do is upload the Marlin.ino file from the Arduino IDE.
Pick the board Arduino/Genuino Mega or Mega 2560 from the boards menu.
Processor Atmega 2560.
I already added the modifed firmware to the main Marlin tree, but also put the modified files in the folder called example_configurations/Alunar_M508.
I used Arduino 1.5.4 on a mac to upload the code to the board. You can find the Arduino IDE here: https://www.arduino.cc/en/Main/OldSoftwareReleases
If you have problems try using a different cable. I had to use a short cable after having some issues.